Your reading into what im saying too hard. I was agreeing with you about Tidus being a dream. What you have to look at is the Fact that this also means that Jecht is too. As with Sin, and the Aeons all products of the Fayth.

But I guess if there were a reasoning the dream thing suits me. I guess you could go as far to say Tidus and Yuna are the same people as Shuyin and Lenne, since machen said lenne and Yuna have the same hand shake. Think its kind of stretching that one out a bit to get that out of it, but its about the easiest explination.
What I was saying that the biggest cooralation between the 4 people is that thier love for each other,losses and and thier search for the ones they lost, are Similar And Shuyin is mistaken for Tidus, and Yuna is mistaken for Lenne as well. I was just saying that it could be a possibility that The two couples are one in the same, but unliekly